Metaphosphate composition



1366- 1956 E. J. GRIFFITH METAPHOSPHATE COMPOSITION Filed March 18, 1955zo twon zou ow om 3 8 4 OO O LIJ OmI om 2 "Jo BHFLLVHHdWHJ.

INVENTOR.

EDWARD J. GRIFFITH.

BY rn s AT United States Patent '0 METAPHOSPHATE COMPOSITION Edward J.Griflith, Dayton, Ohio, assignor to Monsanto Chemical Company, St.Louis, Mo., a corporation of Delaware Application March 18, 1955, SerialNo. 495,317

13 Claims. (Cl. 99--95) potassium or calcium), x and y are positivenumbers,

a is the hydrogen equivalent of M, and ax/y is between and 9. While theprecise structure of the materials is not definitely known, it isbelieved that they are cyclic polymeric materials, which can bedesignated by the formula [MzH1 (P03)aa:+y]n, wherein M, a, x, and y areas defined above and n is a relatively small positive integerprobablysuch that n(ax+y) is equal to less than about ten. Examples ofparticularly useful specific compounds within the scope of the foregoingexpression are sodium hydrogen metaphosphate, [NaH(PO3)2]n, and

disodium hydrogen metaphosphate [Na2H(POs)sln.

The foregoing metaphosphate compositions can be prepared by severalmethods. Typical methods are, for example: (1) by heating sodiumdihydrogen ortho-phosv phate monohydrate and orthophosphoric acid at atemperature above the melting point of the composition, maintaining atthe elevated temperature for a sufiicient length of time to drive offthe appropriate amount of water, and then cooling to obtain the desiredsolid composition; (2) by heating sodium dihydrogen ortho-phosphatemonohydrate and phosphorus pentoxide to a temperature above the meltingpoint of the composition, maintaining this elevated temperature for asufficient length of time to drive off the appropriate amount of water,and then cooling to obtain the desired solid composition; (3) by heatingsodium pentahydrogen orthophosphate (sodium hemi-orthophosphate), toabove its melting point to drive off Water and then cooling to obtainsodium hydrogen metaphosphate; (4) by heating sodium carbonate andphosphorus pentoxide to a temperature above the melting point of thecomposition and in the presence of moisture, and then cooling to obtainthe desired solid metaphosphate composition.

In those reactions (e. g., reactions 1, 2 and 4, above) in which thephosphorus and alkali or alkaline earth metal are introduced in separatereactants, the proportions of such reactants can be varied to give anyof the metaphosphate compositions within the range of the presentinvention. Depending upon the particular proportions chosen, the productmay be'adistinct compound, a eutectic mixture of compounds, or a mixtureof a compound with a eutectic mixture.

A better understanding of the character of the various compositions ofthe present invention can be gained by reference to the drawing, whichis a diagram of phase transition temperatures as a function ofcomposition (expressed in terms of mole proportions of HPOa and NaPOg)for the sodium hydrogen metaphosphate system.

From this phase diagram it can be seen that when sodium 1 2,774,672Patented Dec. 18, 1956 "ice and hydrogen (NaPOa and HPO3) are present inequimolar proportions, a compound is formed. This is the compound[NaH(PO3)2]n, (probably Na2H2(POs)4). At the composition indicated bypoint D, which contains sodium and hydrogen in the atomic proportions of2 to 1, another compound, [N82H(PO3)3]12, is formed. At the compositionsindicated by A, C, and E, constant melting point eutectic mixtures areformed. At the composition indicated by point P, which contains sodiumand hydrogen in the atomic proportions of 3 to 1, the compound,[Na3H(PO3)4]1t, is formed. This compound melts incongruently at theperitectic temperature (about 420 C.). The compositions of proportionsother than A, B, C, D, E and F will be mixtures of the various compoundsand eutectics.

The compositions of the present invention can be obtained either asglassy materials or as crystalline materials, or as mixtures ofcrystalline material in a glassy matrix. The ease with which the variousforms can be obtained varies considerably with such factors as rate ofcooling, composition, etc. For example, it has been found much moredifficult to obtain crystalline solids having lower than a 1:1 atomicratio of sodium/to hydrogen. On the other hand, compositions ofequimolar proportions of NaPOs and HPOs can be quite readilycrystallized by reasonably slow cooling. Where crystallization isdesired, it is often quite helpful to seed a slightly supercooled meltwith previously obtained crystalline material of approximately the samecomposition. 7

' For purposes of simplicity,'the' foregoing description has been setforth with particular emphasis upon metaphosphate compositions in whichthe metal was sodium. It should be understood, however, that ammoniumand other metal cations, or mixtures thereof, can be utilized to givesimilar products. Of particular interest among the other metal cationsare the polyvalent metals, such as aluminum, nickle, iron, cobalt,chromium, titanium, etc., the alkaline earth metals, e. g., calciumstrontium, barium, etc., and other alkali metals, e. g., lithium,potassium, etc. These latter products can be formed by substituting theanalogous metal-containing reactants for the sodium-containing reactantsin the reactions described above. Alternatively, the sodium acidmetaphosphate products can be converted by well-known ion exchangetechniques to the other metal or ammonium acid metaphosphates.

The following examples will serve to illustrate various methods by whichthe compositions of the present invention can be prepared:

EXAMPLE 1 Sodium hydrogen metaphosphate, [NaH(POa)2ln, was prepared bymixing 138 g. of monosodium dihydrogen ortho-phosphate monohydrate and108 g. of a solution weight percent) of phosphoric acid in a platinumdish and stirring until a mollescent mass was obtained. The mixture Wasthen placed in a furnace at 200 C. and maintained there (for about 1 /2hours) until water no longer boiled from the mixture and the mixture hadbecome a clear liquid. The temperature of the furnace was then raised to400 C. and held there (for about 1 hour) until water no longer boiledfrom the mixture. The furnace temperature was then lowered to about 365C. and maintained there for about 4 days while the liquid solidified.The preparation was Withdrawn from the furnace and allowed to cool toroom temperature.

The product was a white non-hygroscopic crystalline solid, and slowlysoluble in cold water. The analyses are given in Table I.

Table I Table III ANALYSES OF PRODUCT F EXAMPLE 1 ANALYSES OF PRODUCT 0FEXAMPLE 02110., as Found, Wt. Cale, as NaH Constituent NaH(PO Percent 5Constituent P002, Wt. Found, Wt.

Wt. Percent Percent Percent EXAMPLE 2' Sodium hydrogen metaphosphate[:NaH(PO'3)2]n, was prepared by mixing 138 g. of monosodium dihydrogenortho-phosphate monohydrate and 71 g. of dry phosphorus pentoxide in aplatinumdish and placing in an oven at 200 C. (for about 6 or 7 hours)until a clear melt was obtained. The temperature was thenraised toabout400 C. and held for 1 hour, and then dropped to about 300 C. and heldfor about 2 days. During the latter time the melt changed toacrystalline solid. The crystalline solid hadthe same physicalcharacteristics as the product of Example 1. Analyses are presented inTable II.

Table II ANALYSES OF PRODUCT OF EXAMPLE 2 Cale, as NaH Constituent (P03):, Wt. Found, TVt.

Percent Percent EXAMPLE 3 Sodium hydrogen metaphosphate[Na'I-I(PO3.)2]n,.was prepared by mixing 124 g. of sodium carbonatemonohydrate. and 142 g. of dry phophorus pentoxide in a platinumcrucible and heating slowly (overthe course of about 1 hour) to 200 C.and holding (for about 1 hour) until the evolution of carbon dioxide hadstopped. The temperature was then raised to about 360 C. and held for 2days, during. which time solid crystalline: sodium hydrogenmetaphosphate was formed.

EXAMPLE 5 Sodium'hydrogen metaphosphate [-NaH(PO3)z]n, was prepared bymixing 138 g. of sodium dihydrogen orthophosphate monohydrate and 108 g.of a solution (85 weight percent) of phosphoric acid were dissolved atroom temperature in 60 g. of water in a platinum crucible. The solutionwas then heated to about 90 C. to evaporate water. As the solutionbecame moreconcentrated, the temperature was raised to keep the solutionmolten. After about 1 /2 hours the. temperature had been raised to about400 C., and it was held at that point for about 1 /2 hours until themelt had stopped boiling. The temperature was then dropped to about 360C. and' held for 2 days, during Which-time sodium hydrogen metaphosphatewas crystallized from the melt. Analysesare presented in Table HI.

X-ray defraction data for this compound appear in table VIII.

EXAMPLE 6' A metaphosphate composition corresponding approximately tothe eutectic composition A of the drawing was prepared by dissolving 69g. of sodium dihydrogen orthophosphate monohydrate in 115 g. of asolution Weight percent) of phosphoric acid in a platinum crucible. Thewater was boiled off (inthe manner described in Example 5), while slowlyraising the temperature to about 400 C. over a period of about 2 hours.The temperature was held at 400 C. ("for about 1 /2 hours) until boilinghad ceased. The melt was then cooled to 365 C. and held for about 2 daysto obtain the solid product.

EXAMPLE 7 A metaphosphate composition corresponding approximately to theeutectic composition C of the drawing was prepared by dissolving 187 g.of sodium dihydrogen ortho-phosphate-monohydrate in g. of a solution (85weight percent) of phosphoric acid in a platinumcrucible. The water wasboiled oil? (in the manner described in Example 5), while slowlyraisingthe temperature to'about 275 C.. over aperiod of' 1 hour. Thetemperature was 'held' at 400 C. (for about 1 hour) until boiling hadceased. The melt was then cooled to 365 C. and held for about 2days-toobtain the solid product. Analyses are presented in Table IV.

A metaphosphate composition correspondingapproximately to the eutecticcomposition E of the drawing was prepared by mixing 33.5 g. of acomposition and 0.28 g. of (-NaPO3)a. The mixture was heated to 600 C.and held for about hour, then reduced to 380 C. and heldfor 1 day. Thecrystalline product analyzed as follows:

T able "V ANALYSES OF PRODUCT 0F EXAMPLE -8 C l u] Constituent a %V't?fiv t if Percent Percent EXAMPLE 9 A metaphosphate compositioncorresponding approximately to the composition G of the drawing wasprepared by dissolving 276 g. of sodium dihydrogen ortho phosphatemonohydrate and 34.6 g. of a solution (85 weight percent) of phosphoricacid in ca. 30 g. of water in a platinum crucible. The water was boiledoff (in the manner described in Example while s'lowly'raising thetemperatureto about 500 C. over a'period of (0a.) 2 hours. Thetemperature was held at 500 C. (for about /2 hour) until boiling hadceased. The melt was then cooled to 400 C. and held for 1 day to obtainthe solid product.

EXAMPLE Disodium monohydrogen metaphosphate [NazH(PO )s]nl pound meltingat about 420 C. and analyzing as follows:

Table VI ANALYSES OF PRODUCT OF EXAMPLE .10

Cale, as Found, Wt. Constituent NazH(PO Percent Wt. Percent Thecharacteristic X-ray difiraction data are presented in Table V111.

EXAMPLE l1 Disodium monohydrogen metaphosphate [NazH (P03 3]nII(insoluble form) was prepared in the case manner as the soluble form(Example 10, above), except that the melt was allowed to crystallize attemperatures above 380 C. This second form of the compound is awaterinsoluble crystalline solid analyzing as follows:

Table VII ANALYSES OF PRODUCT OF EXAMPLE 11 Cale, as N a2 3);, Wt.Percent Found, \Vt.

Constituent Percent OONO The characteristic X-ray difiraction data arepresented in Table VIII.

EXAMPLE 12 Trisodium hydrogen metaphosphate [NasH(POs)4]n, was preparedby mixing 138 g. of NaH2PO4.HzO and 38.4 g. of 85 percent HaPO4 in aplatinum dish. The mixture was heated to 600 C. over the course of onehour, and then allowed to cool to 350 C.

Table VIII X-RAY DIFERACTION DATA I N 3H(PO'3)2 NazH(PO3)sINaiH(POa)z'-II Interplanar Relative Interplanar Relative InterplanarSpac- Spacing, in A. Intensity Spacii Intensity ing, in A. m

5. 16 6. 19 28 7. 053 4. 44 23 5. 43 18 5 262 4. 33 26 5. 01 83 5. 0253. 93 49 4. 4O 6 4. 732 3. 67 15 3. 88 18 4. 396 3. 41 ll 3. 82 28 3.867 3. 39 10 3. 77 36 3. 746 3. 28 8 3. 59 37 3. 527 3. 16 20 3. 47 223. 376 3. 05 100 3. 38 23 3. 255 2. 90 4 3. 27 20 3. 137 2. 63 6 3. 213.074 2. 44 7 3. 11 88 2. 998 2. 34 18 2. 90 57 2. 969

The melt crystallized at this temperature within about twelve hours. Thedesired compound, an insoluble crystalline compound meltingincongruentlyat 420 C., was freed of glassy material by washing with distilled Water.The compound analyzed as follows: 7

Table IX ANALYSES OF PRODUCT OF EXAMPLE 12 Oalc., as Found, Wt.Constituent NazH(PO Percent Wt. Percent EXAMPLE 13 An aluminum acidmetaphosphate Was prepared by mixing 34.9 g. of A1P04 and 230 g. 85percent orthophosphoric acid and heating at 320 C. for two hours. Uponlowering the temperature to 200 C. and holding overnight, the desiredproduct, a white crystalline solid, crystallized from the melt.

Many of the compositions of the present inventio n,

leavening gas, such as carbon dioxide, during the mixing, and baking ofdoughs, thereby causing the dough to The effectiveness of a leaveningcomposition is; determined largely by the total quantity of gas given01f rise.

per unit quantity of leavening agent, and by the conditions under whichthe gas is released.

For example, leavening action, i. e., the release of leavening gas, isprimarily desired during two periods first, in the initial phases ofdough preparation, and second, while the dough is being baked. Thepresently used leavening acids, are generally quite unsatisfactory fromthe point of view of release of leavening gas during both of theseperiods. These latter materials cause the evolution of gas continuouslyfrom the time of first mixing the dry ingredients with moisture untilsubstantially all of the leavening gas has been released. The overallrate of evolution of leavening gas can be sloweddown in order to savemore for the baking period, but this advantage may be attained only atthe expense of decreased leavening. action during the mixing period.

The compositions of the present invention are outstanding leaveningacids in that they not only cause a substantial release of carbondioxide during the initial mixing period, but they also retain asubstantial leavening capacity until such time as the temperature of thedough is elevated, such as during baking. This highly desirable dualstage leavening action (i. e., first during mixing and then duringbaking) is believed to result from the fact that the reaction of theleavening acid with sodium bicarbonate can take place in two differentways.

The first way is by a neutralization reaction between the presentmetaphosphates and sodium bicarbonate. For example, with sodium acidmetaphosphate [NaH(PO3)2] n, the reaction can be indicated as follows:

li e

iltaaol 2.... i.

u A l Na H "-1 Li l.

HIPO NaHCOs NaaHP 04 21120 2002 and/or NBHQPO4 NSHCO; Na2HPO4 E CO2 Thefirst type of leavening action, i. e., the neutralization, takes placereadily at room temperatures and is believed to be the predominantmechanism whereby carbon dioxide is released. The second type ofleavening action, i. e., the hydrolysis, takes place predominantly onlyat elevated temperatures, such as those obtained during baking.

The relative proportions of' the present acid metaphosphates and sodiumbicarbonate to be used inleavening compositions will depend somewhatupon the particular metaphosphate composition chosen; but in general theproportions will be such that the mixture of metaphosphate andbicarbonate will contain between about 25 weight percent and aboutweight percent of metaphosphate and between about 20 weight percent andabout 75 weight percent of bicarbonate. Preferred proportions comprisefrom about 40 weight percent to about 50 weight percent of metaphosphateand from about 50 weight percent to about 60 weight percent ofbicarbonate.

The following examples serve to illustrate the outstanding utility ofthe compositions of the present invention when used in leaveningcompositions with sodium bicarbonate.

EXAMPLE 14 Metaphosphate compositions corresponding approximately to theempirical formulae, Na4Ha(POs)7,

NasH2(PO3)5, Na5I-I2(P0s)7, and NasH(POs)9, were prepared and tested asleavening agents in a standardized biscuit baking test. The weight ratioof leavening acid to sodium bicarbonate in each case was 1.43, 2.0, 2.5and 2.85, respectively. Each of the metaphosphates gave a very definiteleavening action, the first two (i. e., Na4H3(PO3)7, and Na3H2(PO3)5,being particularly effectiveespecially with respect to lightness andvolume of biscuit.

EXAMPLE 15 Comparison with sodium acid pyrophosphate in standard cakebaking test.

Two white cakes were baked under identical conditions except that in onethe leavening acid was sodium hydrogen metaphosphate whereas in theother the leavening acid was sodium acid pyrophosphate. The cakes werethen compared with respect to symmetry, volume, tenderness, texture,color and flavor. sodium hydrogen metaphosphate was as good or betterthan the cake baked with sodium acid pyrophosphate with respect to eachof the foregoing characteristics.

Various acid metaphosphates of this invention are also useful for otherpurposes. For example, some of the insoluble compounds may be used asdental polishing or abrasive agents, particularly in dentifricecompositions. Others are useful as anti-caking agents when added tomaterials such as sugar, etc.

The acid metaphosphates are also useful in the preparation of novelmixed metaphosphate salts of the type MM'y(PO3)a:+y, wherein M, a, x,and y are as defined above and M is a different member selected from thesame group as M. For example, Na2(NH4)2(POs)4, a white crystallinewater-soluble solid, was prepared by dissolving 20 grams of Na2H2(PO3)4in about ml. of water containing twice the stoichiometric amount ofNH4OH required to neutralize the acid phosphate, and precipitating themixed salt by addition of methanol. The mixed salts CaNa2(PO3)4 andK2Na2(POs)4 were made in the same Way, using CaO and KOH.

This application is a continuation-in-part of my earlierfiled copendingapplication Serial No. 398,952, filed December 18, 1953.

I claim:

1. A hydrogen metaphosphate composition having the empirical formula MIH(POa)ae+ wherein M is a member selected from the group consisting of anammonium radical and metal atoms, x and y are positive members, a is thehydrogen equivalent of M, and ax/y is between /2 and 9.

2. A hydrogen metaphosphate composition having the empirical formulaMIHflPOMaew, wherein M is an alkali metal, x and y equal positivenumbers, a equals The cake baked with the the hydrogen equivalent of themetal M, and ax/y is between /2 and 9.

3. A hydrogen metaphosphate composition having the empirical formulaNazHy(PO3)a:+1 wherein x and y are positive numbers, and x/ y is between/2 and 9.

4. Sodium hydrogen metaphosphate.

5. Disodium monohydrogen metaphosphate.

6. Trisodium monohydrogen metaphosphate.

7. A leavening composition comprising sodium bicarbonate and a compoundhaving the empirical for mula, MxHy(PO3)a$+1/, wherein M is an alkalimetal, x and y are positive numbers, a is the hydrogen equivalent of themetal M, and ax/y is between /2 and 9.

8. A leavening composition comprising from 20 weight percent to 75weight percent of sodium bicarbonate and from 25 weight percent to 80weight percent of a metaphosphate having the empirical formula,

wherein x and y are positive numbers and x/y is between /2 and 9.

9. A leavening composition comprising from 20 weight percent to 75weight percent of sodium bicarbonate and 10 from weight percent to 80weight percent of sodium hydrogen metaphosphate.

10. A leavening composition comprising from 20 weight percent to 75weight percent of sodium bicarbonate and from 25 weight percent to 80percent of disodium monohydrogen metaphosphate.

11. A leavening composition comprising from 50 weight percent to 60weight percent of sodium bicarbonate and from weight percent to weightpercent of sodium hydrogen metaphosphate.

12. A hydrogen metaphosphate composition having the empirical formulaMzHy(PO3)ax+y, wherein M is an alkaline earth metal, x and y equalpositive numbers, a equals the hydrogen equivalent of the metal M, andax/y is between /2 and 9.

13. A leavening composition comprising sodium bicarbonate and a compoundhaving the empirical formula, MzHy(PO3)GI+1/, wherein M is an alkalineearth metal, x and y are positive numbers, a is the hydrogen equivalentof the metal M, and ax/ y is between V: and 9.

No references cited.

8. A LEAVENING COMPOSITION COMPRISING FROM 20 WEIGHT PERCENT TO 75WEIGHT PERCENT OF SODIUM BICARBONATE AND FROM 25 WEIGHT PERCENT TO 80WEIGHT PERCENT OF A METAPHOSPHATE HAVING THE EMPIRICAL FORMULA,